Semiconductor packages are electronic devices for accommodating active components such as semiconductor chips, whose structure is primarily composed of a chip mounted on a chip carrier (such as substrate, lead frame, etc.) and electrically connected to the chip carrier by means of conductive elements such as bonding wires; an encapsulant is formed by a resin compound (such as epoxy resin, etc.) on the chip carrier to encapsulate the chip and bonding wires which are protected against external moisture and contaminant. The encapsulant is usually opaque or non-transparent, thereby making a light sensitive or image sensor chip that requires light for operation not suitably incorporated in such a semiconductor package.
Accordingly, a semiconductor package with a structurally modified encapsulant for allowing light to reach a light sensitive chip is provided as illustrated in FIG. 4. In this semiconductor package, a light sensitive chip 20 such as CMOS (complementary metal oxide semiconductor) chip is mounted on a substrate 21 and electrically connected to the substrate 21 by a plurality of bonding wires 22. An encapsulant 23 is formed on the substrate 21 and shaped as a wall structure surrounding the chip 20 and bonding wires 22; this wall-shaped encapsulant 23 forms a cavity 24 where the chip 20 and bonding wires 22 are received and exposed without being encapsulated by the encapsulant 23. An infrared filter 25 and a lens 26 are mounted and supported by the encapsulant 23 to seal an opening of the cavity 24 and hermetically isolate the chip 20 and bonding wires 22 from the external atmosphere, wherein the infrared filter 25 is disposed above the chip 20 and the lens 26 is disposed above the infrared filter 25. The infrared filter 25 and lens 26 are made of light permeable materials to allow light to penetrate therethrough and reach the chip 20 to facilitate operation of the chip 20. This completes fabrication of the semiconductor package.
The above fabricated semiconductor package is subject to a leak test to test if the cavity 24 is hermetically sealed and the chip 20 and bonding wires 22 are hermetically isolated. For example, normally the atmosphere or an ambient environment contains around 500,000 to 1000,000 dust particles, while a clean environment suitable for situating the chip can only contain around 10,000 dust particles. As a result, the chip is processed or mounted on the substrate in a clean room meeting such a low-particle requirement and needs to be isolated from the atmosphere to maintain low content of dust particles and prevent external dusts from contaminating the environment around the chip. In this case, the wall-structured encapsulant 23 surrounding the cavity 24 where the chip 20 is received and the infrared filter 25 and lens 26 sealing the cavity 24 provide such a chip-isolation function, and the leak test is used to test if any leakage occurs from the chip-isolation mechanism in order to assure the low-particle standard being maintained in the cavity 24. If a fabricated semiconductor package fails the leak test, external dust particles may invade the internal environment of the package and contaminate an incorporated chip, thereby making this semiconductor package fail in operation and normally discarded, which would lead to significant waste in costs as one lens costs around USD $1 and also degrade production yield.
Therefore, the problem to be solved herein is to provide a light sensitive semiconductor package which can reduce fabrication costs and improve yield of fabricated package products.